The efficiency of the combustion process in an internal combustion engine can be increased by decreasing the temperature of the air entering the engine for combustion. A decrease in air intake temperature provides a denser intake charge to the engine and allows more air and fuel to be combusted per engine cycle, thereby increasing the output power of the engine. The air intake system in a personal watercraft (PWC) often includes a supercharger for compressing intake air, and an intercooler for cooling the compressed air before delivery to the engine. The intercooler typically comprises a box-like housing enclosing a heat transfer block made of metallic walls defining air and water channels extending through the intercooler. The jet pump of the jet propulsion system for propelling the PWC is used to pump cool lake water through the intercooler water channels. Hot compressed air flowing through the air channels of the intercooler is cooled by heat exchange with cool lake water flowing in the water channels.
While it is convenient to use lake or sea water to cool the air delivered to the engine, the cooling water, especially if it is salt water, can corrode the metallic walls of the water channels, which can reduce the efficacy of the intercooler and, ultimately, lead to failure of part. It is therefore desirable to reduce the corrosion of the intercooler in order to maintain its efficacy and extend its useful life. Typically, intercoolers in PWCs are mounted high within the engine compartment such that, once the PWC is docked, any cooling water that remains is drained out of the intercooler.